Learn how to find umbrian truffels or be an active part of olive harvesting to produce your own native olive oil. Depending on the season. In Umbria, the WHITE TRUFFLE season is from November till January. They aren't found everywhere, mostly they grow along the Tiber river in the north of Umbria. All the varieties of BLACK WINTER TRUFFLES have a nutty flavour and can be found November till February. The best time to harvest OLIVES is between the months of October and December, which is when the olives change colour and become red/violet.